This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. 1. In Stage I, to evaluate the short term safety and tolerability of raltegravir, in HIV infected children and adolescents, added to an initial stable background therapy* which will then be optimized in children and adolescents in the age groups of =2 to <6, =6 to <12 and =12 to <19 years.